Signal comparator system



Oct. 2, 1951 H. R. RElss 2,570,156

SIGNAL COMPARATOR SYSTEM m r HAROLD R.RE|ss N N BY His ATTORNEYS bn/07M Oct. 2, 1951 H. R. REISS SIGNAL COMPARATOR SYSTEM Filed Feb. l5, 1950 FIG.2

DUAL LIMITER TIN RECORDER 2 Sheets-Sheet 2 DUAL LIMITER INVENTOR HAROLD R.REI$S BY HIS ATTORNEYS Patented Oct. 2, 1951 UNITED STATES PATENT OFFICE SIGN-AL ooMPARA'roR; SYSTEM Harold a. Reiss, Philadelphia, Pa.

Application February 13, 1950, Serial No. 143,840l

(Cl. 17e-320) 9-C1aims. l

This invention relates tov a novel signalY com.- parator circuit for use in a system of the character disclosed in my prior application, Serial No.. 16,196, iiled March 22, 1948, whichV system is adapted to determine or measure public reaction to radio and television broadcasts. In such system, audio signals are transmittedy from certain representative radio or television receivers to a central or monitoring station where they are compared with audio signals received directlyT from broadcasting stations. By means of such system, it is possible to determine at any time whether or not each monitored receiver is in operation and, if so, the broadcasting station to which it is tuned'.

In utilizing the above-mentioned system, itis possible to compare the audio Vsignals in various ways, but it has been found from actual practice that it is advantageous to com-parel the signals by means of an electrical comparator which may serve to operate a recorder.

As indicated above, the present invention relates to the signal comparator of such asystem, and this application is a ccntinuation-in-part of the above-mentioned application.

The principal object of the present invention is to provide an improved electrical comparator for the abovementioned purpose.

A further object of the invention` is to provide a signal comparatorv circuit which is highly ein is utilized-in a manner to eilect comparison of the frequency and phase of' two signals. One signal is appliedv via inputV circuit I-I, I2' tothe diagonally. opposed terminals l 3 and I4 of: said.y bridge. while the other signal isY applied via input cir-` cuit I5, I6 to the other pair of diagonally opposed terminals. Il and 181 of the bridge. Preferably, the signals are appliedy to the bridge through push-pull stagesv I9 and 20 of conventional' form which are coupled to the bridge by` means of re sistance-capacitance networks 211 and 22. With this circuit arrangement, one signal kis supplied to the comparator system via conductor 23, while the other signal is supplied via conductor 24; In practice, the signals may be passed through suitable limiting or clipping devices and may be am'- plied prior to application to thecomparator system.

Connected to the bridge I are two output circuits, one output circuit 25, '25'being connected to intermediate points of the opposed bridge arms 2l and 28, and the other output circuit -2 9', -3` being connected to intermediate points of opposed arms 3| and 32. Preferably, the output circuits are connected to cathode follower tubes in' an arrangement now t be described. The output conducto-rs 25 and 26 are connected to the grids of cathode follower rtubes 33 and 34 whichA have a common cathode load circuit 3'5 including a resistor which is preferably variable. "lheoutput conductors 2S and 30 are connected' to the grids of cathode follower tubes 31 and'38' which have a common cathodeload circuit 3!v including a resistor 4D. The necessary plate voltage for the four cathode follower tubes is supplied by means of a common supply conductor 4l from a suitable B+ source.v

The cathode follower tubes may serve t@l con.- trol a relay 42 which, in turn, may control' the circuit 43 of a recorder (not shown). The re-l corder may be of the printing type adapted to print a mark;- on a paper or tape whenever energizedby virtue oi Vthe closure of the circuit 43'. The relay 42 comprises two windings 44 andl 45 acting in oppositionto one another, and a movable contact 4S controlled by said windings yand adapted to close theV circuit 43 when it engages the stationary contact 4l'. The winding v44rk is included in the common cathode load circuit "of tubes 33 and 34, and it is arranged te exert a force on contact 46 tending to'maintain the latter ina circuit-open position. The windings 45. is included in the common cathode load circuit of tubes 31 and 38, and itis arranged kto exert a force on contact 46 tending to move the latter to a circuit-closed position.

Considering, the operationv ofthe system, when the two signals being'compared are not identical in frequency and phase, the force exerted by windingv 44' is sufficient to hold the relay-42i open. This: is accomplished. by suitable adjustment. of resistor 36, and by. virtuev of 'the relative magnitudes of thev two output voltages of bridge te. However, when the two signals being compared are substantially identical in frequency and phase, the outputvoltage across conductors 23 and ilis a maximum, whilethe output voltage across conductors 25 and 26 is a minimum. Consequently, the current flow through the winding 45 is sufficiently great, in comparison to the current flow through winding 44, to close the relay 42, thereby closing the circuit 4'3. Thus, the circuit 43 is closed only when the two signals being compared are substantially identical in frequency and phase.

The bridge system described is well suited for the comparison of two audio frequency signals to determine whether or not the signals are identical, as in a system of the character hereinbefore mentioned for determining public reaction to radio or television broadcasts. By way of example the elements of the system may be as indicated on the drawings.

In Fig. 2, there is shown an alternative form of the signal comparing system which is also disclosed in the aforementioned copending application. Referring to Fig. 2, the two signals to be compared are applied to a dual bridge 48 through push-pull stages 49 and 50, respectively, dual limiters 5| and 52 preferably being provided in the two signal channels. A thyratron 53 is connected to the bridge as shown through a rectifier 54 so as to be triggered whenever the two signals are identical. The thyratron actuates a recording relay 55 which controls suitable recording means (not shown).

A second thyratron 56 is coupled to the bridge 48 as shown and serves to actuate a lock-out relay 51 which, when energized, short circuits the winding of relay 55. The purpose of this arrangement is to prevent actuation of relay 55 except when the two signals are identical.

With the arrangement shown in Fig. 2, when the two applied signals are identical, the voltage applied to the grid of thyratron 53 is a maximum, while the voltage applied to the grid of thyratron 56 is a minimum. Consequently, the thyratron 53 is fired because the voltage applied to its grid is greater than the threshold voltage established by the biasing battery. However, the thyratron 56 is not fired because the voltage applied to its grid is lower than the threshold voltage established by the biasing battery. Under such conditions, the relay 55 is energized While relay 51 is not energized. Therefore, the recorder is actuated by relay 55.

If the two signals applied to the bridge are not identical, the voltage applied to the grid of thyratron 56 will be sufficient to override the bias and fire that thyratron, energizing relay 51. It is unlikely that the voltage applied to the grid of thyratron 53 would be sufficient to override the bias thereof but if it did the relay 55 would not be energized due to the fact that its winding is short circuited through the operation of relay 5T. Thus the thyratron 56 and its associated relay serve to insure that the recorder will not be actuated to give a false indication when the two signals are not identical.

While the invention has been illustrated and described with reference to certain embodiments, it is not limited thereto but is capable of other embodiments and modifications.

I claim:

1. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a four-arm impedance bridge having two pairs of diagonally opposed terminals, a first signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a first output circuit connected to intermediate points of two opposed arms of said bridge, a second output circuit connected to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and means connected to said output circuits for closing said last-recited circuit only in the event of substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

2. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a fourarm impedance bridge having two pairs of diagonally opposed terminals, a first signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a first output circuit connected to intermediate points of two opposed arms of said bridge, a second output circuit connected to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and a relay arranged to control said last-recited circuit and having two windings coupled respectively to said output circuits, whereby to effect closure of the last-recited circuit only in response to substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

3. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a fourarm impedance bridge having two pairs of diagonally opposed terminals, a first signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a first pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of two opposed arms of said bridge, a second pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and means controlled by the load currents of said tubes for effecting closure of the last-recited circuit only in response to substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

4. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a four-arm impedance bridge having two pairs of diagonally opposed terminals, a first signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a first pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of two opposed arms of said bridge, a second pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and a relay arranged to control said last-recited circuit and having two windings included respectively in said cathode load circuits, whereby to effect closure of the last-recited circuit only in response to substantial coincidence oi frequency and phase of two audio signals applied to said input circuits.

5. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a four-arm impedance bridge having two pairs of diagonally opposed terminals, a rst signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a first push-pull stage arranged to supply an audio signal to said input circuit, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a second push-pull stage arranged to supply a second audio signal to said second input circuit, a irst output circuit connected to intermediate points of two opposed arms of said bridge, a second output circuit connected to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and means connected to said output circuits for closing said last-recited circuit only in the event of substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

6. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a four-arm impedance bridge having two pairs of diagonally opposed terminals, a rst signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a first push-pull stage arranged to supply an audio signal to said input circuit, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a second push-pull stage arranged to supply a second audio signal to said second input circuit, a first output circuit connected to intermediate points of two opposed arms of said bridge, a second output circuit connected to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and

means connected to said output circuits for ef-y fecting closure of the last-recited circuit only in response to substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

7. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a fourarm impedance bridge having two pairs of diagonally opposed terminals, a iirst signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a rst push-pull stage arranged to supply an audio signal to said input circuit, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a second push-pull stage arranged to supply a second audio signal to said second input circuit, a first output circuit connected to intermediate points of two opposed arms of said bridge, a second output circuit connected to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and a relay arranged to control said lastrecited circuit and having two windings coupled respectively to said output circuits, whereby to eiiect closure of the last-recited circuit only in response to substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

8. A system for determining and recording substantial coincidence of frequency and phase of two audio signal waves, comprising a fourarm impedance bridge having two pairs of diagonally opposed terminals, a first signal input circuit connected to one pair of diagonally opposed terminals of said bridge, a iirst push-pull stage arranged to supply an audio signal to said input circuit, a second signal input circuit connected to the second pair of diagonally opposed terminals of said bridge, a second push-pull stage arranged to supply a second audio signal to said second input circuit, a first pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of two opposed arms of said bridge, a second pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of the other two opposed arms oi' said bridge, a circuit to be controlled, and means controlled by the load currents oi said tubes I'or eii'ecting closure of the last-recited circuit only in response to substantial coincidence of frequency and phase of two audio signals applied to said input circuits.

9. A system ior determining and recording substantial coincidence or irequency and phase oi two audio signal waves, comprising a :our-arm impedance bridge having two pairs oi diagonally opposed terminals, a nrst signal input circuit connected to one pair oi diagonally opposed terminals oi' said bridge, a nrst push-pull stage arranged to supply an audio signal to said input circuit, a second signal input circuit connected to the second pair or diagonally opposed terminals oil said bridge, a second push-pull stage arranged to supply a second audio signal to said second input cii'cuit, a iirst pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points or' two opposed arms or said bridge, a second pair of cathode follower tubes having a common cathode load circuit and having their control grids connected respectively to intermediate points of the other two opposed arms of said bridge, a circuit to be controlled, and a relay arranged to control said last-recited circuit and having two windings included respectively in said cathode load circuits, whereby to effect closure of the last-recited circuit only in response to substantial coincidence of frequency and phase of two laudio signals applied to said input circuits.

HAROLD R. REISS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,031,509 Seeley Feb. 18, 1936 2,146,526 Bushbeck Feb. 7. 1939 2,169,116 Thompson Aug. 8, 1939 2,283,566 Miller May 19, 1942 2,288,280 Hornbruch June 30, 1942 2,365,218 Rogers Dec. 19, 1944 2,456,199 Lamb Dec. 14, 1948 OTHER. REFERENCES Crosby. Abs. Appl. No. 605,128. August 23, 1949. 

